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1.
Health Commun ; : 1-13, 2024 Aug 27.
Article in English | MEDLINE | ID: mdl-39192551

ABSTRACT

The U.S. Food and Drug Administration (FDA) currently requires a warning about the addictive nature of nicotine to be placed on electronic cigarette advertisements and packaging. To consider the value of additional warning messages on public health outcomes, this study examines the additive effect of new warnings that are based on recent claims from U.S. federal authorities. We conducted a secondary analysis of recent data from 1,202 U.S. youth ages 14-17 to test the impact of exposure to additional warnings placed on advertisements for vaping products on cognitive elaboration, fear, and willingness to vape and smoke. This investigation also looked closely at effects on youth who may have increased risk of future vaping due to prior vaping experiences or having friends who vape. Exposure to the alternative warnings did not amplify cognitive elaboration compared to the current FDA warning alone, but it did increase fear. Youth elaboration on both the benefits and risks of vaping was associated with willingness to both vape and smoke, but fear was not associated with either outcome. The effects of warning label exposure and cognitive elaboration varied by prior vaping experience and having at least one friend who vapes. We conclude by discussing the implications of this contingent pattern of effect and association.

2.
ACS Nano ; 18(24): 15925-15934, 2024 Jun 18.
Article in English | MEDLINE | ID: mdl-38830113

ABSTRACT

The growth in data generation necessitates efficient data processing technologies to address the von Neumann bottleneck in conventional computer architecture. Memory-driven computing, which integrates nonvolatile memory (NVM) devices in a 3D stack, is gaining attention, with CMOS back-end-of-line (BEOL)-compatible ferroelectric (FE) diodes being ideal due to their two-terminal design and inherently selector-free nature, facilitating high-density crossbar arrays. Here, we demonstrate BEOL-compatible, high-performance FE diodes scaled to 5, 10, and 20 nm FE Al0.72Sc0.28N/Al0.64Sc0.36N films. Through interlayer (IL) engineering, we show substantial improvements in the on/off ratios (>166 times) and rectification ratios (>176 times) in these scaled devices. These characteristics also enable 5-bit multistate operation with a stable retention. We also experimentally and theoretically demonstrate the counterintuitive result that the inclusion of an IL can lead to a decrease in the ferroelectric switching voltage of the device. An in-depth analysis into the device transport mechanisms is performed, and our compact model aligns seamlessly with the experimental results. Our results suggest the possibility of using scaled AlxSc1-xN FE diodes for high-performance, low-power, embedded NVM.

3.
ACS Nano ; 18(27): 17958-17968, 2024 Jul 09.
Article in English | MEDLINE | ID: mdl-38918951

ABSTRACT

Achieving robust and electrically controlled valley polarization in monolayer transition metal dichalcogenides (ML-TMDs) is a frontier challenge for realistic valleytronic applications. Theoretical investigations show that the integration of 2D materials with ferroelectrics is a promising strategy; however, an experimental demonstration has remained elusive. Here, we fabricate ferroelectric field-effect transistors using a ML-WSe2 channel and an Al0.68Sc0.32N (AlScN) ferroelectric dielectric and experimentally demonstrate efficient tuning as well as non-volatile control of valley polarization. We measure a large array of transistors and obtain a maximum valley polarization of ∼27% at 80 K with stable retention up to 5400 s. The enhancement in the valley polarization is ascribed to the efficient exciton-to-trion (X-T) conversion and its coupling with an out-of-plane electric field, viz., the quantum-confined Stark effect. This changes the valley depolarization pathway from strong exchange interactions to slow spin-flip intervalley scattering. Our research demonstrates a promising approach for achieving non-volatile control over valley polarization for practical valleytronic device applications.

4.
Development ; 151(10)2024 05 15.
Article in English | MEDLINE | ID: mdl-38775708

ABSTRACT

In utero infection and maternal inflammation can adversely impact fetal brain development. Maternal systemic illness, even in the absence of direct fetal brain infection, is associated with an increased risk of neuropsychiatric disorders in affected offspring. The cell types mediating the fetal brain response to maternal inflammation are largely unknown, hindering the development of novel treatment strategies. Here, we show that microglia, the resident phagocytes of the brain, highly express receptors for relevant pathogens and cytokines throughout embryonic development. Using a rodent maternal immune activation (MIA) model in which polyinosinic:polycytidylic acid is injected into pregnant mice, we demonstrate long-lasting transcriptional changes in fetal microglia that persist into postnatal life. We find that MIA induces widespread gene expression changes in neuronal and non-neuronal cells; importantly, these responses are abolished by selective genetic deletion of microglia, indicating that microglia are required for the transcriptional response of other cortical cell types to MIA. These findings demonstrate that microglia play a crucial durable role in the fetal response to maternal inflammation, and should be explored as potential therapeutic cell targets.


Subject(s)
Brain , Inflammation , Microglia , Poly I-C , Animals , Microglia/metabolism , Microglia/immunology , Female , Pregnancy , Mice , Brain/pathology , Brain/immunology , Brain/metabolism , Inflammation/pathology , Inflammation/genetics , Poly I-C/pharmacology , Fetus , Mice, Inbred C57BL , Gene Expression Regulation, Developmental , Neurons/metabolism
5.
Cell ; 187(13): 3236-3248.e21, 2024 Jun 20.
Article in English | MEDLINE | ID: mdl-38772369

ABSTRACT

Leveraging AAVs' versatile tropism and labeling capacity, we expanded the scale of in vivo CRISPR screening with single-cell transcriptomic phenotyping across embryonic to adult brains and peripheral nervous systems. Through extensive tests of 86 vectors across AAV serotypes combined with a transposon system, we substantially amplified labeling efficacy and accelerated in vivo gene delivery from weeks to days. Our proof-of-principle in utero screen identified the pleiotropic effects of Foxg1, highlighting its tight regulation of distinct networks essential for cell fate specification of Layer 6 corticothalamic neurons. Notably, our platform can label >6% of cerebral cells, surpassing the current state-of-the-art efficacy at <0.1% by lentivirus, to achieve analysis of over 30,000 cells in one experiment and enable massively parallel in vivo Perturb-seq. Compatible with various phenotypic measurements (single-cell or spatial multi-omics), it presents a flexible approach to interrogate gene function across cell types in vivo, translating gene variants to their causal function.


Subject(s)
Gene Regulatory Networks , Single-Cell Analysis , Animals , Female , Humans , Mice , Cerebral Cortex/metabolism , Cerebral Cortex/cytology , CRISPR-Cas Systems/genetics , Dependovirus/genetics , Forkhead Transcription Factors/metabolism , Forkhead Transcription Factors/genetics , Genetic Vectors/metabolism , Mice, Inbred C57BL , Nerve Tissue Proteins/metabolism , Nerve Tissue Proteins/genetics , Neurons/metabolism , Neurons/cytology , Single-Cell Analysis/methods , Transcriptome/genetics , Cell Line , Transcription, Genetic
6.
Mol Cells ; 47(5): 100067, 2024 May.
Article in English | MEDLINE | ID: mdl-38723947

ABSTRACT

The main cause of death in lung cancer patients is metastasis. Thus, efforts to suppress micrometastasis or distant metastasis in lung cancer, identify therapeutic targets and develop related drugs are ongoing. In this study, we identified SET and MYND domain-containing protein 5 (SMYD5) as a novel metastasis regulator in lung cancer and found that SMYD5 was overexpressed in lung cancer based on both RNA-sequencing analysis results derived from the TCGA portal and immunohistochemical analysis results; knockdown of SMYD5 inhibited cell migration and invasion by changing epithelial-mesenchymal transition markers and MMP9 expression in NCI-H1299 and H1703 cell lines. Additionally, SMYD5 knockdown increased Src homology 2-b3 expression by decreasing the level of H4K20 trimethylation. Furthermore, in an in vitro epithelial-mesenchymal transition system using TGF-ß treatment, SMYD5 knockdown resulted in reduced cell migration and invasion in the highly invasive NCI-H1299 and H1703 cell lines. Based on these findings, we propose that SMYD5 could serve as a potential therapeutic target for lung cancer treatment and that cotreatment with an SMYD5 inhibitor and chemotherapy may enhance the therapeutic effect of lung cancer treatment.


Subject(s)
Cell Movement , Epithelial-Mesenchymal Transition , Lung Neoplasms , Humans , Adaptor Proteins, Signal Transducing/metabolism , Adaptor Proteins, Signal Transducing/genetics , Cell Line, Tumor , Epithelial-Mesenchymal Transition/genetics , Gene Expression Regulation, Neoplastic , Lung Neoplasms/pathology , Lung Neoplasms/genetics , Lung Neoplasms/metabolism , Neoplasm Invasiveness
7.
Prev Med Rep ; 42: 102723, 2024 Jun.
Article in English | MEDLINE | ID: mdl-38659997

ABSTRACT

Objective: Vaccination has engendered a spectrum of public opinions, with social media acting as a crucial platform for health-related discussions. The emergence of artificial intelligence technologies, such as large language models (LLMs), offers a novel opportunity to efficiently investigate public discourses. This research assesses the accuracy of ChatGPT, a widely used and freely available service built upon an LLM, for sentiment analysis to discern different stances toward Human Papillomavirus (HPV) vaccination. Methods: Messages related to HPV vaccination were collected from social media supporting different message formats: Facebook (long format) and Twitter (short format). A selection of 1,000 human-evaluated messages was input into the LLM, which generated multiple response instances containing its classification results. Accuracy was measured for each message as the level of concurrence between human and machine decisions, ranging between 0 and 1. Results: Average accuracy was notably high when 20 response instances were used to determine the machine decision of each message: .882 (SE = .021) and .750 (SE = .029) for anti- and pro-vaccination long-form; .773 (SE = .027) and .723 (SE = .029) for anti- and pro-vaccination short-form, respectively. Using only three or even one instance did not lead to a severe decrease in accuracy. However, for long-form messages, the language model exhibited significantly lower accuracy in categorizing pro-vaccination messages than anti-vaccination ones. Conclusions: ChatGPT shows potential in analyzing public opinions on HPV vaccination using social media content. However, understanding the characteristics and limitations of a language model within specific public health contexts remains imperative.

8.
ACS Nano ; 18(5): 4180-4188, 2024 Feb 06.
Article in English | MEDLINE | ID: mdl-38271989

ABSTRACT

Recent advancements in ferroelectric field-effect transistors (FeFETs) using two-dimensional (2D) semiconductor channels and ferroelectric Al0.68Sc0.32N (AlScN) allow high-performance nonvolatile devices with exceptional ON-state currents, large ON/OFF current ratios, and large memory windows (MW). However, previous studies have solely focused on n-type FeFETs, leaving a crucial gap in the development of p-type and ambipolar FeFETs, which are essential for expanding their applicability to a wide range of circuit-level applications. Here, we present a comprehensive demonstration of n-type, p-type, and ambipolar FeFETs on an array scale using AlScN and multilayer/monolayer WSe2. The dominant injected carrier type is modulated through contact engineering at the metal-semiconductor junction, resulting in the realization of all three types of FeFETs. The effect of contact engineering on the carrier injection is further investigated through technology-computer-aided design simulations. Moreover, our 2D WSe2/AlScN FeFETs achieve high electron and hole current densities of ∼20 and ∼10 µA/µm, respectively, with a high ON/OFF ratio surpassing ∼107 and a large MW of >6 V (0.14 V/nm).

9.
bioRxiv ; 2023 Sep 18.
Article in English | MEDLINE | ID: mdl-37790302

ABSTRACT

Systematic analysis of gene function across diverse cell types in vivo is hindered by two challenges: obtaining sufficient cells from live tissues and accurately identifying each cell's perturbation in high-throughput single-cell assays. Leveraging AAV's versatile cell type tropism and high labeling capacity, we expanded the resolution and scale of in vivo CRISPR screens: allowing phenotypic analysis at single-cell resolution across a multitude of cell types in the embryonic brain, adult brain, and peripheral nervous system. We undertook extensive tests of 86 AAV serotypes, combined with a transposon system, to substantially amplify labeling and accelerate in vivo gene delivery from weeks to days. Using this platform, we performed an in utero genetic screen as proof-of-principle and identified pleiotropic regulatory networks of Foxg1 in cortical development, including Layer 6 corticothalamic neurons where it tightly controls distinct networks essential for cell fate specification. Notably, our platform can label >6% of cerebral cells, surpassing the current state-of-the-art efficacy at <0.1% (mediated by lentivirus), and achieve analysis of over 30,000 cells in one experiment, thus enabling massively parallel in vivo Perturb-seq. Compatible with various perturbation techniques (CRISPRa/i) and phenotypic measurements (single-cell or spatial multi-omics), our platform presents a flexible, modular approach to interrogate gene function across diverse cell types in vivo, connecting gene variants to their causal functions.

10.
Health Educ Res ; 38(5): 426-444, 2023 09 20.
Article in English | MEDLINE | ID: mdl-37565566

ABSTRACT

The influences of information exposure on youth and young adults' (YYA) support for smoking/vaping regulations have been understudied. This study examines (i) the relationships between routine exposure to (i.e. scanning) anti-smoking/pro-vaping information and YYA support for anti-smoking/vaping regulations and (ii) whether these relationships differ across YYA users and non-users of tobacco products. We analyzed the data from a nationally representative two-wave rolling cross-sectional survey of YYA in the United States, collected from 2014 to 2017 (baseline n = 10 642; follow-up n = 4001). Less than 5% of the participants ever scanned pro-smoking and anti-vaping information. Scanning anti-smoking information had significant positive relationships with support for all anti-smoking policies cross-sectionally, and this pattern was longitudinally significant in two anti-smoking policy contexts. Scanning pro-vaping information had significant negative associations with support for anti-vaping policies cross-sectionally, but not longitudinally. The lagged positive relationships between scanning anti-smoking information and support for anti-smoking regulations were stronger among YYA smokers than among YYA non-smokers, whereas evidence from adult data suggested the opposite pattern. The findings suggest that scanning information can affect YYA support for tobacco regulations. Future efforts are required to investigate mechanisms underlying the influences of scanned information on YYA support for tobacco regulations.


Subject(s)
Tobacco Products , Humans , Adolescent , Young Adult , United States , Tobacco Control , Cross-Sectional Studies , Smokers
11.
Hum Mol Genet ; 32(18): 2773-2786, 2023 09 05.
Article in English | MEDLINE | ID: mdl-37384417

ABSTRACT

De novo heterozygous loss-of-function mutations in phosphatase and tensin homolog (PTEN) are strongly associated with autism spectrum disorders; however, it is unclear how heterozygous mutations in this gene affect different cell types during human brain development and how these effects vary across individuals. Here, we used human cortical organoids from different donors to identify cell-type specific developmental events that are affected by heterozygous mutations in PTEN. We profiled individual organoids by single-cell RNA-seq, proteomics and spatial transcriptomics and revealed abnormalities in developmental timing in human outer radial glia progenitors and deep-layer cortical projection neurons, which varied with the donor genetic background. Calcium imaging in intact organoids showed that both accelerated and delayed neuronal development phenotypes resulted in similar abnormal activity of local circuits, irrespective of genetic background. The work reveals donor-dependent, cell-type specific developmental phenotypes of PTEN heterozygosity that later converge on disrupted neuronal activity.


Subject(s)
Autism Spectrum Disorder , Neurons , Humans , Neurons/metabolism , Cell Differentiation , Organoids/metabolism , Autism Spectrum Disorder/genetics , Mutation , PTEN Phosphohydrolase/genetics
12.
Nat Nanotechnol ; 18(9): 1044-1050, 2023 Sep.
Article in English | MEDLINE | ID: mdl-37217764

ABSTRACT

Three-dimensional monolithic integration of memory devices with logic transistors is a frontier challenge in computer hardware. This integration is essential for augmenting computational power concurrent with enhanced energy efficiency in big data applications such as artificial intelligence. Despite decades of efforts, there remains an urgent need for reliable, compact, fast, energy-efficient and scalable memory devices. Ferroelectric field-effect transistors (FE-FETs) are a promising candidate, but requisite scalability and performance in a back-end-of-line process have proven challenging. Here we present back-end-of-line-compatible FE-FETs using two-dimensional MoS2 channels and AlScN ferroelectric materials, all grown via wafer-scalable processes. A large array of FE-FETs with memory windows larger than 7.8 V, ON/OFF ratios greater than 107 and ON-current density greater than 250 µA um-1, all at ~80 nm channel length are demonstrated. The FE-FETs show stable retention up to 10 years by extension, and endurance greater than 104 cycles in addition to 4-bit pulse-programmable memory features, thereby opening a path towards the three-dimensional heterointegration of a two-dimensional semiconductor memory with silicon complementary metal-oxide-semiconductor logic.

13.
Nat Nanotechnol ; 18(5): 422-441, 2023 May.
Article in English | MEDLINE | ID: mdl-37106053

ABSTRACT

Ferroelectric materials, the charge equivalent of magnets, have been the subject of continued research interest since their discovery more than 100 years ago. The spontaneous electric polarization in these crystals, which is non-volatile and programmable, is appealing for a range of information technologies. However, while magnets have found their way into various types of modern information technology hardware, applications of ferroelectric materials that use their ferroelectric properties are still limited. Recent advances in ferroelectric materials with wurtzite and fluorite structure have renewed enthusiasm and offered new opportunities for their deployment in commercial-scale devices in microelectronics hardware. This Review focuses on the most recent and emerging wurtzite-structured ferroelectric materials and emphasizes their applications in memory and storage-based microelectronic hardware. Relevant comparisons with existing fluorite-structured ferroelectric materials are made and a detailed outlook on ferroelectric materials and devices applications is provided.

14.
J Health Commun ; 27(7): 495-509, 2022 07 03.
Article in English | MEDLINE | ID: mdl-36205037

ABSTRACT

Misinformation about COVID-19 vaccines is widely available in the public communication environment. Exposure to the misinformation may increase perceived risk of and evoke negative emotions toward COVID-19 vaccines that may eventually reduce COVID-19 vaccination intentions. The negative influences of misinformation may vary by aspects of individuals' social networks. Expanding the reasoned action approach, we proposed a comprehensive model to examine the roles of misinformation beliefs, perceived risk, fear, worry, and social networks in explaining COVID-19 vaccination intentions. We tested the model using survey data of South Korean adults, collected when the Korean government launched its nationwide vaccination program in April 2021 (n = 744). The results from our step-by-step path analyses indicated that COVID-19 vaccination intentions had positive direct associations with vaccination-specific factors such as attitudes toward, injunctive norms on, and perceived behavioral control over COVID-19 vaccination. Perceived risk was also directly linked to intentions. Among these factors, attitudes and injunctive norms were most strongly related to intentions. Misinformation beliefs and worry had negative indirect relationships with intentions via the mediation of these variables directly connected to intentions. The negative influences of misinformation beliefs were greater among respondents reported stronger tie strengths. Theoretical and practical implications were discussed.


Subject(s)
COVID-19 , Intention , Adult , Humans , COVID-19 Vaccines , COVID-19/prevention & control , Vaccination/psychology , Communication
15.
ACS Appl Mater Interfaces ; 14(41): 46876-46883, 2022 Oct 19.
Article in English | MEDLINE | ID: mdl-36194531

ABSTRACT

Organic/inorganic heterostructures present a versatile platform for creating materials with new functionalities and hybrid properties. In particular, junctions between two dimensional materials have demonstrated utility in next generation electronic, optical, and optoelectronic devices. This work pioneers a microwave facilitated synthesis process to readily incorporate few-layer covalent organic framework (COF) films onto monolayer transition metal dichalcogenides (TMDC). Preferential microwave excitation of the monolayer TMDC flakes result in selective attachment of COFs onto the van der Waals surface with film thicknesses between 1 and 4 nm. The flexible process is extended to multiple TMDCs (MoS2, MoSe2, MoSSe) and several well-known COFs (TAPA-PDA COF, TPT-TFA-COF, and COF-5). Photoluminescence studies reveal a power-dependent defect formation in the TMDC layer, which facilitates electronic coupling between the materials at higher TMDC defect densities. This coupling results in a shift in the A-exciton peak location of MoSe2, with a red or blue shift of 50 or 19 meV, respectively, depending upon the electron donating character of the few-layer COF films. Moreover, optoelectronic devices fabricated from the COF-5/TMDC heterostructure present an opportunity to tune the PL intensity and control the interaction dynamics within inorganic/organic heterostructures.

16.
Cell ; 185(20): 3770-3788.e27, 2022 09 29.
Article in English | MEDLINE | ID: mdl-36179669

ABSTRACT

Realizing the full utility of brain organoids to study human development requires understanding whether organoids precisely replicate endogenous cellular and molecular events, particularly since acquisition of cell identity in organoids can be impaired by abnormal metabolic states. We present a comprehensive single-cell transcriptomic, epigenetic, and spatial atlas of human cortical organoid development, comprising over 610,000 cells, from generation of neural progenitors through production of differentiated neuronal and glial subtypes. We show that processes of cellular diversification correlate closely to endogenous ones, irrespective of metabolic state, empowering the use of this atlas to study human fate specification. We define longitudinal molecular trajectories of cortical cell types during organoid development, identify genes with predicted human-specific roles in lineage establishment, and uncover early transcriptional diversity of human callosal neurons. The findings validate this comprehensive atlas of human corticogenesis in vitro as a resource to prime investigation into the mechanisms of human cortical development.


Subject(s)
Cerebral Cortex , Organoids , Cell Differentiation , Cerebral Cortex/metabolism , Humans , Neurogenesis , Neurons , Organoids/metabolism
17.
Nature ; 608(7924): 750-756, 2022 08.
Article in English | MEDLINE | ID: mdl-35948630

ABSTRACT

Microglia are specialized macrophages in the brain parenchyma that exist in multiple transcriptional states and reside within a wide range of neuronal environments1-4. However, how and where these states are generated remains poorly understood. Here, using the mouse somatosensory cortex, we demonstrate that microglia density and molecular state acquisition are determined by the local composition of pyramidal neuron classes. Using single-cell and spatial transcriptomic profiling, we unveil the molecular signatures and spatial distributions of diverse microglia populations and show that certain states are enriched in specific cortical layers, whereas others are broadly distributed throughout the cortex. Notably, conversion of deep-layer pyramidal neurons to an alternate class identity reconfigures the distribution of local, layer-enriched homeostatic microglia to match the new neuronal niche. Leveraging the transcriptional diversity of pyramidal neurons in the neocortex, we construct a ligand-receptor atlas describing interactions between individual pyramidal neuron subtypes and microglia states, revealing rules of neuron-microglia communication. Our findings uncover a fundamental role for neuronal diversity in instructing the acquisition of microglia states as a potential mechanism for fine-tuning neuroimmune interactions within the cortical local circuitry.


Subject(s)
Microglia , Neocortex , Pyramidal Cells , Somatosensory Cortex , Animals , Cell Count , Mice , Microglia/classification , Microglia/physiology , Neocortex/cytology , Neocortex/physiology , Pyramidal Cells/classification , Pyramidal Cells/physiology , Single-Cell Analysis , Somatosensory Cortex/cytology , Somatosensory Cortex/physiology , Transcriptome
18.
Nat Neurosci ; 25(8): 1049-1058, 2022 08.
Article in English | MEDLINE | ID: mdl-35915179

ABSTRACT

Mammalian neocortical neurons span one of the most diverse cell type spectra of any tissue. Cortical neurons are born during embryonic development, and their maturation extends into postnatal life. The regulatory strategies underlying progressive neuronal development and maturation remain unclear. Here we present an integrated single-cell epigenomic and transcriptional analysis of individual mouse and marmoset cortical neuron classes, spanning both early postmitotic stages of identity acquisition and later stages of neuronal plasticity and circuit integration. We found that, in both species, the regulatory strategies controlling early and late stages of pan-neuronal development diverge. Early postmitotic neurons use more widely shared and evolutionarily conserved molecular regulatory programs. In contrast, programs active during later neuronal maturation are more brain- and neuron-specific and more evolutionarily divergent. Our work uncovers a temporal shift in regulatory choices during neuronal diversification and maturation in both mice and marmosets, which likely reflects unique evolutionary constraints on distinct events of neuronal development in the neocortex.


Subject(s)
Neocortex , Animals , Callithrix , Mammals , Mice , Neurogenesis/physiology , Neuronal Plasticity , Neurons/physiology
19.
ACS Nano ; 16(6): 9651-9659, 2022 Jun 28.
Article in English | MEDLINE | ID: mdl-35621266

ABSTRACT

Two-dimensional chalcogenide semiconductors have recently emerged as a host material for quantum emitters of single photons. While several reports on defect- and strain-induced single-photon emission from 2D chalcogenides exist, a bottom-up, lithography-free approach to producing a high density of emitters remains elusive. Further, the physical properties of quantum emission in the case of strained 2D semiconductors are far from being understood. Here, we demonstrate a bottom-up, scalable, and lithography-free approach for creating large areas of localized emitters with high density (∼150 emitters/um2) in a WSe2 monolayer. We induce strain inside the WSe2 monolayer with high spatial density by conformally placing the WSe2 monolayer over a uniform array of Pt nanoparticles with a size of 10 nm. Cryogenic, time-resolved, and gate-tunable luminescence measurements combined with near-field luminescence spectroscopy suggest the formation of localized states in strained regions that emit single photons with a high spatial density. Our approach of using a metal nanoparticle array to generate a high density of strained quantum emitters will be applied to scalable, tunable, and versatile quantum light sources.

20.
ACS Nano ; 16(6): 8827-8836, 2022 Jun 28.
Article in English | MEDLINE | ID: mdl-35435652

ABSTRACT

A rapid surge in global energy consumption has led to a greater demand for renewable energy to overcome energy resource limitations and environmental problems. Recently, a number of van der Waals materials have been highlighted as efficient absorbers for very thin and highly efficient photovoltaic (PV) devices. Despite the predicted potential, achieving power conversion efficiencies (PCEs) above 5% in PV devices based on van der Waals materials has been challenging. Here, we demonstrate a vertical WSe2 PV device with a high PCE of 5.44% under one-sun AM1.5G illumination. We reveal the multifunctional nature of a tungsten oxide layer, which promotes a stronger internal electric field by overcoming limitations imposed by the Fermi-level pinning at WSe2 interfaces and acts as an electron-selective contact in combination with monolayer graphene. Together with the developed bottom contact scheme, this simple yet effective contact engineering method improves the PCE by more than five times.

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